1. Field of the Invention
The present invention relates to a differential unit with a limited slip differential mechanism provided with clutch plates for receiving clutch engaging force applied to a friction clutch member at a planetary carrier side surface.
2. Description of the Related Art
Conventionally, it is known to use a planetary gear mechanism as a center differential for a full-time four-wheel drive vehicle. There are also many instances in this type of center differential where a limited slip differential mechanism is provided for appropriately performing torque distribution by limiting differential action between front and rear wheels according to torque acting on the center differential.
For example, Japanese patent laid-open No. 2004-225716 discloses a differential unit provided with a torque sensing limited slip differential mechanism. With the technology disclosed in this document, a wet-type multiple disc clutch is provided as a friction clutch member at one side of a planetary carrier constituting the planetary gear mechanism, and by varying clutch engaging force for the wet-type multiple disc clutch according to input torque it is possible to suitably perform torque distribution to front and rear wheels.
Limited differential torque for limiting differential action of the differential unit in this manner is determined by the clutch engaging force for the friction clutch. As technology for engaging a friction clutch, it is common to have a structure where a pair of clutch plates are provided either side of the friction clutch, with one clutch plate being pressed against the other clutch plate and fastening the friction clutch between the two clutch plates, to cause rotation of the friction plate together with the two clutch plates.
In the case one clutch plate integrally formed in a ring gear may be divided from the ring gear. The clutch plate receiving clutch engaging pressure can be supported by the planetary carrier of the planetary gear mechanism so as to receive clutch engaging pressure in stead of the ring gear. But the clutch plate is provided between the planetary carrier and the other clutch plate, the clutch plate and the planetary carrier are rotated relative to each other, it is not possible to sufficiently limit differential action of the planetary gear mechanism.